Powder metal components such as crankshaft main bearing caps, for example, have been produced by using a powder metallurgical press and sinter operation. A density of a component produced using the powder metallurgical single press and sinter operation is typically in the range of about 6.4 to 7.0 gm/cc. The higher the density, the higher the mechanical properties observed in the component. However, the density reached in the component is a function of the number of processing steps involved, as well as a press tonnage available.
Generally, the density varies from position to position in the component. Usually the density is higher near surfaces. Therefore, a top flat surface as well as a bottom flat surface of a component will exhibit higher density values when compared to the density values at a mid-section.
Ever increasing higher engine horse power and torque requirements cause higher operational loads to be exerted on a crankshaft bearing cap. For this reason, lower density locations, positions, or regions in the bearing cap may become susceptible to an over-stressed condition, which may result in a reduction of fatigue life of the bearing cap. To avoid crack initiation and eventually its propagation, lower density locations, positions, or regions need to be strengthened. One option is to have a press capable of forming the component at the desired density. However, depending on the manufacturer, the press tonnage available, and the complexity of the component, that may not be always possible.
Since the mid-section of the bearing cap is lower in density and correspondingly higher in porosity, various methods have been investigated. Some of the methods include single needle programmable pattern peening of a bolted face peened area, over-burnishing of the bolt holes, and forming the threads rather than cutting the threads for side bolted end caps.
It would be desirable to produce a powdered metal component, wherein the component can be efficiently and accurately reinforced.